Conventionally, the evolution in the radio access system and radio network of cellular mobile communication (hereinafter, referred to as “Long Term Evolution” (LTE) or “Evolved Universal Terrestrial Radio Access” (EUTRA)) and the radio access system and radio network (hereinafter, referred to as “Long Term Evolution-Advanced” (LTE-A) or “Advanced Evolved Universal Terrestrial Radio Access” (A-EUTRA)), which realize higher-speed data communication using a frequency band wider than that of LTE, have been under study in the third Generation Partnership Project (3GPP).
In LTE, orthogonal frequency division multiplexing (OFDM) system which is multicarrier transmission is used as the communication system of radio communication from a base station apparatus to a mobile station apparatus (downlink). Moreover, as the communication system of the radio communication from a mobile station apparatus to a base station apparatus (uplink), SC-FDMA (Single-Carrier Frequency Division Multiple Access) system which is single carrier transmission is used.
In LTE, on a downlink, a synchronization channel (SCH), a physical broadcast channel (PBCH), a physical downlink control channel (PDCCH), a physical downlink shared channel (PDSCH), a physical multicast channel (PMCH), a physical control format indicator channel (PCFICH), and a physical HARQ indicator channel (Physical Hybrid automatic repeat request Indicator Channel; PHICH) are allocated. On an uplink, a physical uplink shared channel (PUSCH), a physical uplink control channel (PUCCH), and a physical random access channel (PRACH) are allocated.
The purposes of using the physical random access channel are to establish synchronization between a mobile station apparatus and a base station apparatus on an uplink and to request for the allocation of radio resources of the uplink. When the mobile station apparatus and the base station apparatus are out of synchronization, when the mobile station apparatus has data information to be transmitted to the base station apparatus by means of a physical uplink shared channel, or when the base station apparatus notifies the mobile station apparatus by means of a physical downlink control channel so as to start random access procedure, the mobile station apparatus activates random access.
There are two access methods for random access: contention based random access and non-contention based random access. The contention based random access is an access method which may cause collision between mobile station apparatuses, and is the typically performed random access. The non-contention based random access is an access method which does not cause collision between the mobile station apparatuses, and is the random access which is performed at the initiative of a base station apparatus in a special case, such as during handover, in order to establish synchronization between the mobile station apparatus and the base station apparatus.
In the random access, the mobile station apparatus transmits only a preamble in order to establish synchronization. The preamble includes a signature which is a signal pattern representing information. Here, several tens of types of signatures are prepared so as to be able to represent several bits of information. At present, a mobile station apparatus is assumed to transmit 6 bits of information using the preamble, and 64 types of signatures are assumed to be prepared.
FIG. 16 is a view showing an example of the procedure of the contention based random access according to a conventional art. First, a mobile station apparatus 1, based on the downlink channel quality or the like, determines a range of signatures to be selected, and randomly selects a signature from the selected range of signatures and transmits a preamble by means of a physical random access channel (Message 1 (M1)).
A base station apparatus 3, upon receipt of the preamble transmitted from the mobile station apparatus 1, calculates, from the preamble, a deviation in synchronization timing between the mobile station apparatus 1 and the base station apparatus 3, and performs scheduling (allocation of radio resources of an uplink, and specifying of a transmission format (message size) and the like) for the mobile station apparatus 1 to transmit Message 3. Then, the base station apparatus 3 allocates a temporary C-RNTI (Cell-Radio Network Temporary Identifier) to the mobile station apparatus 1, and arranges an RA-RNTI (Random Access-Radio Network Temporary Identifier) corresponding to a physical random access channel having received the preamble, into the physical downlink control channel, and transmits a random access response including deviation information of the synchronization timing, scheduling information, the temporary C-RNTI, and the number (also referred to as a random ID or a preamble ID) of a signature of the received preamble, by a physical downlink shared channel which the radio resource allocation included in the physical downlink control channel indicates (Message 2 (M2)).
After confirming that the physical downlink control channel includes the RA-RNTI, the mobile station apparatus 1 confirms the content of the random access response arranged in the physical downlink shared channel which the radio resource allocation included in the physical downlink control channel indicates. Then, the mobile station apparatus 1 extracts the response including the number of the signature of the preamble which the mobile station apparatus 1 transmitted, corrects the deviation in synchronization timing, and transmits Message 3 including information, such as a connection request, by means of the allocated radio resource and transmission format of the physical uplink shared channel (Message 3 (M3)).
The base station apparatus 3, upon receipt of the Message 3 from the mobile station apparatus 1, transmits to the mobile station apparatus 1 a contention resolution indicating that the mobile station apparatus 1 has succeeded in random access, i.e., no collision of preambles has occurred between the mobile station apparatuses 1, or indicating that the mobile station apparatus 1, when a collision of preambles is occurring between the mobile station apparatuses 1, has overcome the collision of preambles (Message 4 (M4)).
If having succeeded in receiving the contention resolution, the mobile station apparatus 1 determines that the random access is successful, and terminates the processing related to the random access. Note that, if not having detected the number of a signature of the transmitted preamble within a random access response receiving period, or if not having detected the contention resolution within a contention resolution receiving period, the mobile station apparatus 1 starts again from the transmission of the preamble.
FIG. 17 is a view showing an example of the procedure of the non-contention based random access according to the conventional art. First, the base station apparatus 3 notifies the mobile station apparatus 1 of the information indicating the number of a signature and the radio resource of a physical random access channel, using a physical downlink control channel and the like. The mobile station apparatus 1 transmits a preamble including a signature of the number notified from the base station apparatus 3, by means of the physical random access channel notified from the base station apparatus 3 (Message 1 (N1)).
The base station apparatus 3, upon receipt of the preamble including the signature of the number notified to the mobile station apparatus 1, calculates from the preamble a deviation in synchronization timing between the mobile station apparatus 1 and the base station apparatus 3. Then, the base station apparatus 3 arranges, into the physical downlink control channel, an RA-RNTI corresponding to a physical random access channel having received the preamble, and transmits a random access response including the deviation information of synchronization timing and the number of a signature of the received preamble to a physical downlink shared channel which the radio resource allocation included in the physical downlink control channel indicates (Message 2 (N2)).
After confirming that the physical downlink control channel includes the RA-RNTI, the mobile station apparatus 1 confirms the content of the random access response arranged in the physical downlink shared channel which the radio resource allocation included in the physical downlink control channel indicates. Then, if the content includes the number of the signature of the preamble which the mobile station apparatus 1 transmitted, the mobile station apparatus 1 determines that the random access is successful, and terminates the processing related to the random access (see Non-Patent Document 1, Paragraph 5.1).
In LTE-A, there is a need for backward compatibility with LTE, in other words, there is a need to enable a base station apparatus of LTE-A to simultaneously perform radio communication with mobile station apparatuses of both LTE-A and LTE and also enable a mobile station apparatus of LTE-A to perform radio communication with base station apparatuses of both LTE-A and LTE. Therefore, it is under study that LTE-A uses the same channel structure as LTE does.
For example, in LTE-A, a technique (also referred to as spectrum aggregation, carrier aggregation, frequency aggregation, or the like) has been proposed for using a plurality of frequency bands (hereinafter, referred to as carrier components (CC) or component carriers (CC)), each having the same channel structure as that of LTE, as one frequency band (wide frequency band).
Specifically, in communications using the frequency aggregation, for each downlink carrier component, a physical broadcast channel, a physical downlink control channel, a physical downlink shared channel, a physical multicast channel, a physical control format indicator channel, and a physical HARQ indicator channel are transmitted, and for each physical uplink carrier component, a physical uplink shared channel, a physical uplink control channel, and a physical random access channel are allocated. That is, the frequency aggregation is a technique, wherein on an uplink and on a downlink, a base station apparatus and a plurality of mobile station apparatuses simultaneously transmit/receive a physical uplink control channel, a physical uplink shared channel, a physical downlink control channel, a physical downlink shared channel, and the like together with a plurality of pieces of data information or a plurality of pieces of control information using a plurality of carrier components (see Non patent literature 2, Chapter 5).